International cooperation led by USA elected officials is usually a terrible thing, for Americans and also for everyone else. I don't know exactly how we're going to get fucked over by this. Based on previous form, it will likely involve exporting particular pro-corporate folly to other nations who unlike USA previously have avoided those particular follies. Also, since they're not exactly hiding the inherent coercion involved, there will likely be sanctions and stupid wars. After all, those are the answer to literally every problem everywhere, according to USA war media. In addition, it's a good bet there will be special pleading for favored and infamously badly-behaved USA mega-corps like Boeing and Wal-Mart.
If USA politicians actually wanted international standards of corporate taxation, they would copy what works from EU and also from other well-run modern states. Instead they claim to want those other nations to copy our dismal shit system.
Of course, that is stupid. That loophole is what happens now, and the point of such a treaty would be tariffs or sanctions against non signatories.